Answer:
B) a substance's color and odor changed Explanation: A signal that a chemical change has occurred is when its odor (its smell) or its appearance has changed.
Answer:
HgO (empirical formula)
Explanation:
4.08 - 3.78 = 0.3g (oxygen)

0.02 : 0.02
0.02/0.02 : 0.02/0.02
1 : 1 (ratio)
HgO ( empirical formula)
2HgO ----> 2Hg + O2 ( your equation correct)
Robert A. Millikan and Harvey Fletcher performed the oil drop experiment.
Answer: About 0.20 grams of copper (II) is formed, and some aluminum is left in the reaction mixture
Answer:
839 g
Explanation:
We know we will need a balanced equation with masses and molar masses, so let’s gather all the information in one place.
M_r: 81.97 209.94
NaAlO₂ + … ⟶ Na₃AlF₆ + …
Mass/g: 2150
1. Calculate the <em>moles of Na₃AlF₆
</em>
Moles of Na₃AlF₆ = 2150 × 1/209.94 Do the operation
Moles of Na₃AlF₆ = 10.24 mol Na₃AlF₆
2. Calculate the <em>moles of NaAlO</em>₂
The molar ratio is 1 mol NaAlO₂:1 mol Na₃AlF₆
Moles of NaAlO₂ = 10.24 × 1/1 = 10.24 mol NaAlO₂
3. Calculate the <em>mass of NaAlO₂
</em>
Mass of NaAlO₂ = 10.24 × 81.97 Do the multiplication
Mass of NaAlO₂ = 839 g